ISO date format

The International Organization for Standardization (ISO) date format is a standard way to express a numeric calendar date that eliminates ambiguity. For example, North Americans usually write the month before the date. Europeans write the date before the month as in "30.3.1998" for March 30, 1998. The separators used between numbers also vary between countries. The question of how to express a date in numbers that precedes "1/1/1" also arises (how to express a date that is "B.C."). ISO 8601 provides a standard cross-national approach that says:

• A general-to-specific approach, forming a date that is easier to process - thus, the year first, followed by month, then day
• With each separated by a hyphen ("-")
• Numbers less than 10 preceded by a leading zero
• Years expressed as "0" prior to year 1 and as "-1" for the year prior to year 0 (and so forth)

To express whether the date reflects the Julian calendar or the Gregorian calendar , the date can be followed with a "J" or a "G".